The shoot apical meristem restores its symplasmic organization during chilling-induced release from dormancy

Rinne, PLH Kaikuranta, PM van der Schoot, C

Plh. Rinne et al., The shoot apical meristem restores its symplasmic organization during chilling-induced release from dormancy, PLANT J, 26(3), 2001, pp. 249-264

73

INGLESE

Article

Plant Sciences","Animal & Plant Sciences

PLANT JOURNAL

0960-7412 → ACNP

26

3

2001

249 - 264

ISI

0960-7412(200105)26:3<249:TSAMRI>2.0.ZU;2-7

The shoot apex of overwintering perennials ceases its morphogenetic activit y at the end of the growing season and transforms into a bud which is dorma nt and freezing-tolerant, In birch (Betula pubescens) these events are trig gered by short photoperiod, and involve the production of 1,3-beta -D-gluca n containing sphincters on the plasmodesmata. As a result, all symplasmic p athways shut down. Here we show that breakage of bud dormancy by chilling i nvolves restoration of the symplasmic organization of the meristem. This re storation is likely to be mediated by 1,3-beta -D-glucanase, which was pres ent in small spherosome-like vacuoles that arose de novo during dormancy in duction. During chilling these vacuoles were displaced from the bulk cytopl asm to the cortical cytoplasm where they became aligned with the plasma mem brane, often associated with plasmodesmata. At this stage the enzyme also a ppeared outside the vacuoles. During chilling, 1,8-beta -D-glucan disappear ed from the plasmodesmal channels and wall sleeves, and the plasmodesmata r egained the capacity for cell-cell transport, as demonstrated by microinjec tion of Lucifer Yellow CH and Fluorescein-tagged gibberellic acid. Collecti vely, the present experiments demonstrate that restoration of the symplasmi c organization of the meristem is indispensable for the release of buds fro m dormancy and the assumption of a proliferation-competent state, and impli cate 1,3-beta -D-glucanase action at the plasmodesmata. Based on these find ings we propose a model for 'dormancy cycling' which depicts the meristem a s passing through three sequential states of cellular communication with ch aracteristic sensitivities to distinct environmental cues.